A nice hostel with friendly staff at reception (and somewhat less friendly at breakfast). Free Wi-Fi, quite good (for a hostel in Paris) breakfast, lockers in the rooms.
The district is amazingly calm for such a location. Staff is OK. However, the furniture is old (new is only TV screen which I don't need), sheets and floor are dirty. Ground floor rooms give to the court, and there are people going in and out of neighbouring buildings. Good point: there is a bath, not just a shower.
David is very nice person and living on the boat is unforgettable experience, especially if it is in summer. For winter, it is rather cold. You also need to take into account that boat is a little bit aside from center, and for getting into/out of it, you need to have no physical constraints or handicaps.